Fig. 1.

Hydrolytic activity of Bv-PPase. Dependencies of the PP_i hydrolysis rate on Na⁺ concentration in the absence and presence of 50 mM K⁺ (A) and K⁺ concentration in the presence of 50 mM Na⁺ (B) at two pH values. (C) pH dependence of the PP_i hydrolysis rate, measured at 10 mM Na⁺ and 50 mM K⁺. PP_i concentrations in µM were 1,550, 474, 234, 169, 158, 149, 143, 141, and 140 µM at pH 5.5, 6.0, 6.5, 7.0, 7.2, 7.5, 8.0, 8.5, and 9.0, respectively. The buffers were MES- (pH 5.5–6.5), MOPS- (pH 6.5–8.0), TAPS- (pH 8.0–9.0), or CAPSO-TMA₄OH (pH 9.0).